Process for preparing lead alloys



Patented My 21, 1942 s'mras rnocnss yon PREPARING Ln armors of New YorkNo Drawing. Application February 10, 1949, Serial No.-3l8,368. inGermany February 29, 1939 10 Claims. (01. 75-157.

- kaline earth metals by reacting an alkaline earth metal carbide withmolten lead, which requires less time than previously necessary.

It is a special object of the invention to provide a process forpreparing lead alloys containing alkaline earth metals by reacting analkaline earth metal carbide wherein a novel covering flux or slag isemployed which increases the alloying speed.

In the specification and claims the term alkaline earth metals isemployed to designate piagnesium, as well as calcium, barium andstronium.

It has already been proposed to prepare lead alloys containing alkalineearth metals by introducing an alkaline earth metal carbide into amolten bath of lead provided with a covering flux or slag composed offused salts. Halides, such as, calcium fluoride, carnallite, calciumchloride, alkali metal chlorides and mixtures of alkaline earth metalhalides and alkali metal halides, have been employed as the coveringflux or slag. It was especially advantageous to employ mixtures ofchlorides or fluorides of two or three alkaline earth metals so as tolower the melting point of the covering fluxor slag. I

It has now been found, in accordance with the present invention, thatthe addition of a relatively small quantity of metallic aluminum to thecovering flux or slag causes an extraordinary increase in the speed ofreaction when treating molten lead with alkaline earth metal carbides.The aluminum is preferably added in the form of granules and inquantities less than 1% by weight of the lead treated. The addition ofthe aluminum to the fused salt covering layer may take place eitherbefore or simultaneously with the addition of the alkaline earth metalcarbides to the molten lead.

The following example serves to illustrate the invention, but theinvention is in no way limited thereto:

Example A molten bath to 12 tons of lead is coving 88% of calciumchloride and 12% of calcium fluoride. To this layer to kg. of granularaluminum are'added. 1250 kg. of calcium carbide are added to the moltenbath of lead and the mixture is stirred. After 3 to 4 hours thereactionis complete and a lead alloy is obtained containing 6% of calcium.

When carrying out the process under the same conditions but without theaddition of aluminum, 8 to 9 hours are required to form a lead alloycontaining only 4% to 5% of calcium. The addition of aluminum has beenfound advantageous with all types of iusedsalt mixtures suitable ascovering fluxes for the lead bath during the reaction. For example,covering fluxes containing an alkaline earth metal halide, mixtures ofalkaline earth metal halides and mixtures of alkaline earth metalhalides with alkali metal halides may be employed in accordance with thepresent process. It is especially advantageous if the salt .mixtureswere so selected that changes in the composition thereof occurringduring the conversion of the alkaline earth metal carbide and theformation of the lead alloy would lower their melting points.

a mixture of 10% of CaCl2 and 90% BaCla may be employed with specialadvantage for the salt mixture of the covering flux, as during thetreatment of the molten lead bath covered thereby with calcium carbideand the melting point of such salt mixture is lowered. This depressionof the melting point is caused as a portion of the calcium obtained bythe decomposition of calthe proportion of calcium chloride in thecovering flux approaches that necessary for a eutectic mixture of 09.012and BaCla. The free barium produced by this reaction is taken up by thelead.

When covering fluxes are employed containing one or more hygroscopicsalts, the addition of aluminum thereto has still a ,further advantagein that it efiects dehydration of such covering fluxes. It is veryimportant that the covering fluxes employed for the process aresubstantially dehydrated upon the addition of the alkaline earth metalcarbide as any water which may be present decomposes the carbide to forman alkaline earth oxide and acetylene. The forma tion of the alkalineearth oxide is highly undesirable as such oxide no longer contains thealkaline earth metal in a form available for the formation of an alloywith the lead. Furtherered with 1700 kg. of. a fused salt layercontainmore, the calcium oxide decreases the fluidity of the coveringflux which renders it more difficult to separate the lead alloy from thecovering flux after completion of the process and which renders thelosses of the alloy higher as small globules thereof remain suspended insuch 5' flux.

The addition of aluminum to covering fluxes containing alkaline earthmetal salts which are very difiicult to dehydrate completely by theapplication of heat alone, such as calcium chloride, effects completedehydration of such cov-' ering fluxes and therefore prevents thedecomposition of the alkaline earth metal carbides to form oxides whichwould be caused by the presence of the water. The aluminum may be addedto the covering fluxes before the introduction of the alkaline earthmetal carbides into the molten lead bath or simultaneously therewith.

, While we have described herein some embodi- 'ments of our invention byway of example, we go wish it to be understood that we do not intend tolimit ourselves thereby, except within the scope of the appended claims.

We claim:

1. In a .process for the preparation of leadalkaline earth metal alloyswhich comprises introducing an alkaline earth metal carbide into amolten bath of lead provided with a suitable fused salt covering flux,the improvement which comprises adding metallic aluminum to the coveringflux.

2. In a process for thepreparation of leadalkaline earth metal alloyswhich comprises introducing an alkaline earth metal carbide into amolten bath of lead provided with a suitable fused salt covering flux,the improvement which comprises adding metallic aluminum to the coveringflux before the alkaline earth metal carbide is introduced into themolten lead bath.

3. In a process for the preparation of lead- 40 alkaline earth metalalloys which comprises introducing an alkaline earth metal carbide intoa molten bath of lead provided with a suitable fused salt covering flux,the improvement which com-prises adding metallic aluminum to thecovering flux while simultaneously introducing the alkaline earth metalcarbide into the molten lead bath.

4. In a process for the preparation of leadalkaline earth metal alloyswhich com-prises introducing an alkaline earth metal carbide into amolten, bath of lead provided with a suitable [fused salt covering flux,the improvement which comprises adding granular metallic aluminum to thecovering flux.

5. A process for the preparation of lead-alkaline earth metal alloyscomprising adding an alkaline earth metal carbide to a bath of moltenlead provided with a fused salt covering flux containing a mixture ofalkaline earth metal halides and metallic aluminum. I

6. A process for the preparation of lead-alkaline earth metal alloyscomprising adding an alkaline earth'metal carbide to a bath of moltenlead provided with a fused salt covering flux containing a mixture ofalkaline earth metal halides and alkali metal halides and metallicaluminum.

7. A .process for the preparation of lead-alkaline earth metal alloyscomprising adding an alkaline earth metal carbide to a bath-of moltenlead provided with a covering flux containing a salt mixture of suchcomposition that the change in its composition during the preparation ofthe lead alloy lowers its melting point, and metallic aluminum.

8. In a process for the preparation of leadalkaline earth metal alloyswhich comprises introducing an alkaline earth metal carbide into amolten bath of lead provided with a suitable fused'salt covering fluxcontaining hygroscopic salts, the improvement which comprises addingmetallic aluminum to the covering flux to dehydrate the covering flux. I

9. In a process for the preparation of leadalkaline earth metal alloyswhich comprises in-,'

troducing an alkaline earth metal carbide into a molten bath of leadprovided with a suitable fused salt covering flux, the improvement whichv comprises adding metallic aluminum to the covering flux in a quantityless than 1% by weight of the lead to be alloyed.

10. A process for the preparation of lead-alkaline earth metal alloyscomprising introducing an alkaline earth metal carbide into a bath of1000 to ,1200 parts by weight of molten lead provided with a coveringflux containing parts by weight of a salt mixture containing 88% ofcalcium .chloride and 12% of calcium fluoride and 2.5 to 3 parts byweight of metallic aluminum.

JOHANN SIEGENS. OSKAR; RODER.

